Utils: Introduce GlobalFileChangeBlocker

Tracks application state, and signals when it is changed.

Supports forcing blocked state with reference counting.

Change-Id: Ic173d42446b1b08bd4a1e7c1acf38c68644d30b3
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cpptools/cppmodelmanager.h

@@ -230,8 +230,6 @@ public:
 
     void renameIncludes(const QString &oldFileName, const QString &newFileName);
 
-    void setBackendJobsPostponed(bool postponed);
-
 signals:
     /// Project data might be locked while this is emitted.
     void aboutToRemoveFiles(const QStringList &files);